The 411 on a 408

Without a doubt big cubes are addictive. Teaming up with Wynnespeed, the goal was to build a tough street/strip 408 that would make 530-plus lb-ft and about 520 hp with these numbers escalating to about 800 and 700 respectively when the nitrous comes in. Big inches need big cylinder head airflow numbers. Courtesy of Brodix 1, we now have some M2 CNC-ported heads that have not only the flow (307 cfm in., 224 cfm ex.@.700 lift) but also have just about ideal port sizes for this 408 build to peak at the 6,000-rpm target required.

Along with that the intake port, though still less than a typical V-8 GM head, also had more swirl than is usually found with most Ford heads. As originally pointed out by Wynnespeed's boss Todd Wynne, the M2 Track 1s had all the ingredients as the basis for a conventional (near stock port positions) out-of-the-box build for a large inch small-block. After hammering out the spec with Todd, here is what we decided on for a motor with true street driveability.

The Short-Block
To get 408 inches from a basic 351 requires a 4.03 bore (.030 over stock) and a 4-inch stroke (1/2-inch over stock). For a serious build like this, Wynnespeed checks out the block candidate for core shift and general casting thickness. It has to be a good stock block to be acceptable. If any more than 700 hp is called for then a sportsman or race block will be the way to go. Once a decision is made on the block, Wynnespeed bores, decks (to zero piston/deck height) and otherwise preps the block as required.

In addition to all the regular stuff for our block this meant drilling and tapping the holes in the valley for OE-style hydraulic roller lifters and cutting the block for rod clearance with the 4-inch stroke. Important at this level of power were the ARP main bearing studs and a steel mains girdle. The rotating assembly was to comprise of a Scat Forged crank (internally balanced to cut main bearing loads), Scat rods, Diamond pistons and an ATI crank damper.

After receiving our engine kit from Wynnespeed, crewchief/engine builder Mervynn Bonnet and I went through and checked all the component fits and limits. Everything proved to be right where it should be which made our assembly job straightforward. If you don't already have them, two tools you should invest in are a tapered piston/ring installer and a proper damper installer.

Cam And Valvetrain--Select And Install
Once again, Motor Machine & Supply using their Cam Master program did our cam selection on the computer. For our first build with this engine it was decided to use a non-nitrous biased cam so as to fully realize this 408's low-speed output. The intent here was to use this engine as a cam test unit to demonstrate the differences produced when both bigger and nitrous-orientated cams were used.

For the initial build the cam called for was a Comp Cams 3316 Xtreme Energy profile (288 seat duration--236@.050) on both intake and exhaust ground on a 106-degree lobe centerline angle and at 4 degrees advance. With a set of Comp's 1.7:1-ratio aluminum roller rockers (#1049-16) this cam gave a theoretical 590 thousandths valve lift thus giving us access to over 300 cfm of air on the intake and 210 on the exhaust.

To make the job of changing cams easier it was decided to use a Jesel beltdrive for the cam. In addition to making life easier when cam testing there is a small power advantage with a beltdrive and also some additional damping of crank torsional and bending moments. If your budget extends to it and you decide to go the beltdrive route follow the assembly shown in the nearby photos.

The next job to do was to time the CC cam into the specs given by Motor Machine Cam master program. Why do this if the cam is adjustable and can be power timed on the dyno? The answer here is to test how accurate the MM&S spec is. If they are on the money any adjustments we do on the dyno should not show a gain. If this is the case this will be good news for any of you getting an MM&S Cam Master spec and not having the benefit of an adjustable cam drive as we have here. It looks like Comp, Jesel and Scat did their job of making the parts accurately, because our cam timing tolerance stack up amounted to nothing with the cam coming in on the zero mark on the Jesel beltdrive.

The next move was to install the Brodix Track 1 heads and then to determine the pushrod length required. The heads went on with Fel-pro competition head gaskets and ARP head bolts. When high valve lifts are used (this engine will utilize up to 650-thousandths lift during our subsequent cam testing) it becomes imperative to minimize valve stem side loads so as to hold guide wear to a minimum. To do this the pushrod length used was that which gave the smallest and most centered wipe pattern on the end of the valves. This is not always the same length as that which produces most lift. In our case, the theoretical lift possible with 1.7:1 rockers and the 347-thousandths lift on the cam was 590 thousandths. What was seen with a pushrod for maximum lift was 588 thousandths and for the most centered pattern and minimum sweep was 582 thousandths.

Intake Manifold: Carb & Nitrous
The intake manifold used for the Wynnespeed 408 was an out-of-the-box, or nearly so, Edelbrock Super Victor. Essentially this is a Victor Jr. with larger ports. When it came time to install the manifold it was found that though the port runners were at the manifold face, the right size for a near perfect match to the Brodix M2 heads, the position was too high. To achieve alignment some 50 thousandths had to be machined off each face. Because we were assembling the engine in my shop this was a job we had to take care of. The same will apply if you elect to build a Wynnespeed 408 from a kit. However, if Wynnespeed assembles your motor such machining as is required to match the intake is part of the build.

Because of no less than superb results on past motors the choice of fuel delivery was by means of one of Barry Grant's Demon carbs--in this instance an 850 Race Demon. Because this engine was to be nitrous injected nothing was spared in terms of fuel delivery to the carb and nitrous system.

Our car was to be equipped with a big BG fuel pump capable of delivering enough fuel for at least 1,500 hp. To make sure the fuel pressure to both the carb and the N2O system was controlled within tight limits, a BG by-pass style regulator was used. This is incorporated into BG's superb adjustable-length fuel log. The nitrous system was from Nitrous Express. A choice again based on excellent past experience. Because for long term reliability, a self imposed 700hp limit was set for this 408's total output and all the power boosting requirements could be more than handled by a simple 200hp kit jetted to deliver about 150-175hp increase.

Headers And Pan Install
The class that it was intended to race our car in called for headers of no more than 1 3/4 inches on the primary. While this was just about an optimal size for the Wynnespeed 408 in non-nitrous mode it is most certainly too small to deal with the copious quantities of exhaust produced by the 408's normally induced air and that of a 150hp-plus shot of nitrous.

This entailed choosing a header that made the very best of the flow capabilities of 1 3/4-inch tubing. This meant having as large a sweeping bends as possible with no collapsing of the tubes in those bends. Along with this all the butt-welded joints in the individual pipes had to be done right so as not to ingress into the tube and cause unwanted flow restriction. In short it needed a quality header to get the job done.

Regular readers will know that here at MM&FF we have had excellent results from Kook's headers. They are certainly not the cheapest, but good stuff never is. Although you can get them from Kook's in coated form those for the 408 were, at my request, sent in their "raw" state. This was done for two reasons; the first is it is not uncommon to get small (and sometimes not so small) interference problems between headers and the oil pan. This necessitates making changes to the pan, the headers or both. Secondly, Calico Coating is a very competent coating company less than 50 miles from my shop and my before and after dyno tests on their coatings have shown they work.

Before getting the headers coated a trial assembly of our Moroso pan and Kook's headers was made to see if there was any interference. The good news is the Kook's headers/Moroso pan combo fit together with no problems. Indeed the only adjustments that were needed in this department were some minor tweaking of the oil pickup tube due to the mains girdle form. This was easily accomplished with a large rubber mallet. A check of the pan to pickup clearance was made using clay in a plastic bag placed on the mesh of the pickup.

After tightening down the pan and removing it the clay indicated about 7/16 clearance was present, which was right in the middle of the recommended 3/8 to 1/2 inch called for by Moroso. With no header-to-pan clearance problems to deal with all that was left to do was to install and route the dipstick tube. This fit conveniently as seen in the nearby photos.

Ignition And Ancillaries
In spite of designing electronic equipment when I worked in the aerospace industry, I always suffered with what could best be described as wiring dyslexia. To me a wiring harness is a giant bundle of plastic spaghetti and represents nothing more than confusion. That is one of the reasons why I opted, once again, to use Performance Distributors GM HEI-style distributor adaption for the small-block Ford. Not only does it deliver a big fat spark to a 60-thousandths-plus plug to some 9,000 rpm, but also it takes only a single wiring connection to make it all happen.

Add to this the near zero spark scatter and the micro adjuster for fine tuning and you can see why excellent results have been achieved on the past three engines I have used such units on. Given the engine spec Performance Distributors tailored the advance curve to what would be required. They have been doing this so long now (try over 30 years) that probably 99 times out of a 100 they hit the nail right on the head. Since our motor fit into a fairly common spec nothing different was expected in this case. The dyno will, of course, be the last authority here.

For plug wires ACCEL's spiral core 8mm stuff was used. A point here is with so many different head and header styles the choice of plug boot is not so simple as it might seem. A boot requirement can range anywhere from 90 degrees to straight and the lengths of the wires in kits always seem to present problems when trying to make the whole deal look tidy.

A near straight boot looked to be the way to go for the head and header combination on the 408. To meet the needs I used ACCEL's adjustable boot universal kit for an HEI distributor. This allowed me to put about a 15-degree bend in the boot and cut the cables to the desired length to make a tidy loom. For a water pump a CSI unit was decided on. These have enough capacity to meet the needs of a continuous duty cycle so there was no worry about being up to the job of totally dealing with a drag racing street cruiser. In fact, CSI has enough confidence in the capabilities of their pump that we are working with them on an electric system for road race applications. Normally this pump would be a direct bolt-on deal if a regular chain drive to the cam had been employed. In our case it was necessary, with the Jesel beltdrive unit, to run either an adaptor spacer between the CSI pump and Jesel drive or modify the pump outlets to suit. Having access to a Bridgeport mill I opted for the second route with everything fitting as shown nearby.

Next on the list was to install the ATI damper. Again this was a piece used because of its known functionality. Sure this might be a $450 damper, but if it keeps the crank in a $10,000 motor then it is cheap insurance. Most of the Winston Cup teams use ATI dampers and if you want to know about building high-performance reliability that is where the most effective answers are found.

The last job of any significance was to address the throttle linkage and nitrous activation switch location. Here I used one of AED's quality throttle bracket kits. Up to this point it was all plain sailing, but installing the micro switch for the nitrous presented a problem. AED's bracket for the job fit a Holly, but the bosses and tapped holes used did not exist on a Demon carb. I did not manage to find anything off the shelf so I ended up making a little gismo that clamped onto the AED throttle linkage plate. With that done this Wynnespeed 408 was ready for the dyno.